Requirements Definition

The Requirements Definition Statement

The requirements definition statement—usually just called the requirements definition—is a straightforward text report that simply lists the functional and nonfunctional requirements in an outline format. For example, the DrōnTeq IS department prepared a requirements definition statement when the current Drone Sales System was developed several years ago. Figure 3‐3 shows the partial contents of this document.

As shown in Figure 3‐3, requirements are typically identified by numbering. Assigning unique numbers enables each requirement to be tracked through the entire development process. For clarity, the requirements are typically grouped into functional and nonfunctional groupings. Then, within each of those groups, they are classified further by the type of requirement or by business area.

Sometimes, requirements are prioritized on the requirements definition statement. They can be ranked as having “high,” “medium,” or “low” importance in the new system, or they can be labeled with the version of the system that will address the requirement (e.g., release 1, release 2, release 3). This practice is particularly important with RAD methodologies that deliver requirements in batches by developing incremental versions of the system.

The most obvious purpose of the requirements definition is to provide a clear statement of what the new system should do in order to achieve the system vision described in the system request. The use cases, process models, and data models provide additional explanatory content in different formats. A critically important purpose of the requirements definition, however, is to define the scope of the system. The document describes to the analysts exactly what the final system needs to do. In addition, it serves to establish the users' expectations for the system. If and when discrepancies or misunderstandings arise, the document serves as a resource for clarification.